Open Characterization of 2.5 Micron, Particulate-Borne Semi-Volatile Organic Compounds by GC-TOFMS and UHPLC Orbitrap MS: Method Development, Performance and Applications

Importance of the Topic

Ambient fine particulate matter smaller than 2.5 micron transports semi-volatile organic compounds that impact air quality and human health. Detailed chemical profiling of these SVOCs is essential to understand mutagenic and endocrine disrupting risks associated with urban pollution.

Objectives and Study Overview

This work aimed to demonstrate a conceptual workflow for monitoring ambient SVOCs on PM2.5 filters collected by a tapered element oscillating microbalance. The strategy combined targeted and non targeted analysis using gas chromatography time of flight mass spectrometry and ultra performance liquid chromatography coupled to Orbitrap mass spectrometry.

Methodology

• Sampling: PM2.5 was collected on 15 mm TEOM filters over 60 days at two urban sites with industrial and commercial activities at a flow rate of 3 L per minute.
• Extraction: Filters were ultrasonically extracted twice for 15 minutes with acetonitrile, filtered, concentrated to near dryness, reconstituted in acetonitrile and stored at low temperature until analysis.
• Data Analysis: GC-TOFMS data were deconvoluted using proprietary software and spectral libraries for targeted PAHs. UHPLC Orbitrap MS data were screened with TraceFinder using pesticide and emerging pollutants databases. Identification criteria included mass accuracy within 2 ppm, isotopic peak ratios, and retention time matching when standards were available.

Used Instrumentation

• Thermo Scientific TEOM tapered element oscillating microbalance for PM2.5 sampling
• LECO Pegasus III GC-TOFMS with DB-5 column and helium carrier gas
• Thermo Scientific Dionex UltiMate 3000 UHPLC system with BetaSil and coreshell C18 columns
• Thermo Scientific Exactive Plus Orbitrap mass spectrometer with heated electrospray ionization source operated in positive and negative modes

Main Results and Discussion

Targeted PAH analysis detected multi ring compounds such as phenanthrene and pyrene at variable loadings between sites, while low boiling two and three ring PAHs often broke through the sampling media and were below detection. UHPLC Orbitrap screening identified bisphenol A in most samples and nicotine in nine of ten samples, highlighting the presence of endocrine disruptors and tobacco smoke markers. Over fifty non targeted pesticides and pharmaceuticals were tentatively detected, though some identifications such as gemfibrozil proved false positives due to retention time discrepancies. Accurate mass and isotopic patterns improved confidence but require MS/MS confirmation for definitive assignment.

Benefits and Practical Applications

This combined high resolution workflow enables comprehensive chemical profiling of ambient particulate SVOCs. It supports environmental monitoring programs, source apportionment studies, and regulatory compliance testing. The approach offers high sensitivity for both targeted and emergent contaminants in urban and industrial settings.

Future Trends and Opportunities

Advances in high resolution tandem mass spectrometry and automated data mining will enhance specificity and reduce false positives. Expansion of spectral libraries, integration of MS/MS fragmentation criteria, and adoption of suspect screening will broaden the scope of detectable compounds. Real time or near real time monitoring and machine learning driven pattern recognition may further refine airborne SVOC assessments.

Conclusion

The study demonstrates that TEOM filter sampling combined with GC-TOFMS and UHPLC Orbitrap MS, supported by iterative high resolution data analysis, provides a powerful platform for open characterization of particulate borne SVOCs. The methodology yields both targeted and non targeted pollutant profiles, informing air quality management and health risk evaluations.

References

• Ontario Ministry of the Environment Method E3480 determination of PAHs by GC-TOFMS
• Ontario Ministry of the Environment Method E3454 determination of emerging organic pollutants by LC-MS/MS
• SANCO 12495/2011 method validation and quality control for pesticide residue analysis